The present invention concerns a drive system for centrifugal processing apparatus.
Centrifugal processing systems are used in many fields. In one important field of use, a liquid having a suspended mass therein is subjected to centrifugal forces to obtain separation of the suspended mass.
As a more specific example, although no limitation is intended herein, in recent years the long term storage of human blood has been accomplished by separating out the plasma component of the blood and freezing the remaining blood cell component in a liquid medium, such as glycerol. Prior to use, the glycerolized red blood cells are thawed and pumped into the centrifugating wash chamber of a centrifugal liquid processing apparatus. While the red blood cells are being held in place by centrifugation, they are washed with a saline solution which displaces the glycerol preservative. The resulting reconstituted blood is then removed from the wash chamber and packaged for use.
The aforementioned blood conditioning process, like other processes wherein a liquid is caused to flow through a suspended mass under centrifugation, necessitates the transfer of solution into and out of the rotating wash chamber while the chamber is in motion. Thus while glycerolized red cell and saline solution are passed into the wash chamber, waste and reconstituted blood solutions are passed from the chamber. To avoid contamination of these solutions, or exposure of persons involved in the processing operation to the solutions, the transfer operations are preferably carried out within a sealed flow system.
One type of centrifugal processing system which is well adapted for the aforementioned blood conditioning process uses the principle of operation described in Dale A. Adams U.S. Pat. No. 3,586,413. The apparatus of the Adams patent establishes fluid communication between a rotating chamber and stationary reservoirs through a flexible interconnecting umbilical cord without the use of rotating seals, which are expensive to manufacture and which add the possibility of contamination of the fluid being processed.
The primary embodiment of the Adams patent comprises a rotating platform which is supported above a stationary surface by means of a rotating support. A tube is connected to the stationary support along the axis of the rotating platform and the rotating support, with the tube extending through the rotating support and having one end fastened to the axis of the rotating platform. A motor drive is provided to drive both the rotating platform and the rotating support in the same relative direction at speeds in the ratio of 2:1, respectively. It has been found that by maintaining this speed ratio, the tube will be prevented from becoming twisted. An improvement with respect to this principle of operation, comprising a novel drive system for a centrifugal liquid processing system, is disclosed in Khoja, et al. U.S. Pat. No. 3,986,442. In the Khoja, et al. patent, a novel drive system is provided for driving a rotor assembly at a first speed and a rotor drive assembly at one-half the first speed, in order to prevent an umbilical tube from becoming twisted.
While the Adams patent broadly suggests driving the rotating support to allow the tube to provide the necessary torque for driving the rotating platform, it has been discovered that this tube drive principle can be utilized with centrifugal processing apparatus by employing an umbilical tube formed of tubular material having a dynamic stiffness between 0.1 in..sup.2 pounds and 100 in..sup.2 pounds. In this manner, the processing chamber forms an idling member which does not require a direct drive by an external device or gears from the primary motor-shaft drive system.
Thus by using a stiff tubular material for the umbilical tube, the processing chamber will follow the driving rotation of such tube to automatically rotate at twice the speed of the tube. The advantage of a non-twisting tube will be maintained with the internal complexity of the centrifuge processing apparatus being significantly reduced. As a further result, the reduction in drive components greatly reduces cleaning requirements and simplifies the loading of software.
It is, therefore, an object of the present invention to provide centrifugal processing apparatus in which the processing chamber follows the driving rotation of an umbilical cable segment and thus requires no external direct drive mechanism.
A further object of the present invention is to provide a centrifugal processing apparatus which is simplified in construction and is efficient to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.